IBM Selectric Maintenance Manual page 29

2. I Shift Clutch Ratchet Adjustment (Late) (Fig. 29.1) - Ad-
just the shift clutch ratchet to satisfy the following con-
dition. With the machine turned off and the shift cam
detented, the shift clutch ratchet will rotate .028" to
.050" when the shift release arm releases the ratchet.
The rotation can be observed relative to the shift re-
lease arm and the shift cam stop. Be sure to loosen the
set screw in the ratchet before adjusting. Remove play
from the shift ratchet in a clockwise direction. Note:
The C-7 cam must be removed to make the above adjust-
ment.
• 028" to .050"
FIGURE 29. I Shift Clutch Ratchet Adjustment
The adjustment of the shift clutch ratchet determines
how much the clutch spring will be expanded when the
shift mechanism is at rest. Expanding the spring too
much may cause failure of the cam to reach the detent-
ed position, because the spring would be expanded too
soon. Insufficient expansion would allow the clutch
spring to drag when at rest creating a load on the motor
and on the shift release mechanism.
3.
Shift Cam Stop - Adjust the stop so that the shift clutch
ratchet has .010" to .030" rotary motion between the
shift cam stop and the shift release arm with the mech-
anism at rest (Fig. 30).
The adjustment insures that the shift cam will not be al-
lowed to travel past the detented position •
Shift Release Arm Holding Inner Lug
Of Ratchet
Maintain Clearance
• 010" To .030"
4.
NOTE: The stop should not bind against the spring
clutch when the adjustment is made.
CAUTION: Be sure the cam is detented at the time the
stop adjustment is checked.
Shift Cam Brake (Fig. 31) - The shift cam brake shall be
so adjusted, that the shift cam wi II stop in the center of
the detent position ± .015" when the detent roller is
held away from the cam during the shift from upper case
to lower case •
FIGURE 31 • Shift Cam Brake Adjustment
Excessive braking action cou Id prevent the cam from
reaching the detented position in the lower case. Insuf-
ficient braking action would result in a noisy shift oper-
ation and expose the mechanism to possible parts break-
age.
Here To Clutch FIGURE 32. Shift Interlock
Spring
FIGURE 30. Shift Cam Stop Adjustment
2-8
5. Shift Interlock
a. With the shift interlock on the high point of the cam,
adjust the interlock by its adiusting screw so that the
tip just bottoms between two teeth on the shift clutch
ratchet (Fig. 32).